Method of forming deep trench isolation in radiation sensing substrate and image sensor device

ABSTRACT

A method of forming a deep trench isolation in a radiation sensing substrate includes: forming a trench in the radiation sensing substrate; forming a corrosion resistive layer in the trench, in which the corrosion resistive layer includes titanium carbon nitride having a chemical formula of TiC x N (2-x) , and x is in a range of 0.1 to 0.9; and filling a reflective material in the trench and over the corrosion resistive layer.

RELATED APPLICATIONS

This application is a divisional of and claims priority to U.S. patentapplication Ser. No. 15/048,936, titled “METHOD OF FORMING DEEP TRENCHISOLATION IN RADIATION SENSING SUBSTRATE AND IMAGE SENSOR DEVICE” andfiled Feb. 19, 2016, which claims priority to U.S. ProvisionalApplication Ser. No. 62/261,204, titled “METHOD OF FORMING DEEP TRENCHISOLATION IN RADIATION SENSING SUBSTRATE AND IMAGE SENSOR DEVICE” andfiled Nov. 30, 2015. U.S. patent application Ser. No. 15/048,936 andU.S. Provisional Application Ser. No. 62/261,204 are herein incorporatedby reference.

BACKGROUND

Semiconductor image sensors are used to sense radiation such as light.Complementary metal-oxide-semiconductor (CMOS) image sensors (CIS) andcharged-coupled device (CCD) sensors are widely used in variousapplications such as digital camera or mobile phone camera applications.These devices utilize an array of pixels in a substrate, includingphotodiodes and transistors, to absorb radiation projected towards thesubstrate and convert the sensed radiation into electrical signals.

A backside-illuminated (BSI) image-sensor device is one type ofimage-sensor device. The BSI image-sensor device is used for sensing avolume of light projected towards a backside surface of a substrate(which supports the image sensor circuitry of the BSI image-sensordevice). The pixel grid is located at a front side of the substrate, andthe substrate is thin enough so that light projected towards thebackside of the substrate can reach the pixel grid. The BSI image-sensordevice provides a high fill factor and reduced destructive interference,as compared to frontside-illuminated (FSI) image-sensor devices.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A to 1E are cross-sectional views at various stages of forming adeep trench isolation (DTI) in a radiation sensing substrate inaccordance with some embodiments of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

A common defect of an image sensor device is optical cross talk.“Optical cross talk” refers to photon interference from neighboringpixels that degrades light sensing reliability and accuracy of thepixels. In some embodiments, a deep trench isolation (DTI) is formed ina radiation sensing substrate to prevent undesired optical cross talk.

In some embodiments, a reflective material, such as metal (e.g.,tungsten) or alloy, is formed in the deep trench or over the radiationsensing substrate to increase reflected area. However, when thereflective material is formed (e.g., using chemical vapor deposition),the radiation sensing substrate may be damaged. The damage of theradiation sensing substrate may lead to excessive amount of currentleakage, and thus causes abnormally high signal from the pixels to formwhite pixels. Therefore, the present disclosure provides a method offorming a deep trench isolation in a radiation sensing substrate, whichincludes forming a corrosion resistive layer in a trench to protect theradiation sensing substrate when a reflective material is formed.Embodiments of the method of forming the deep trench isolation in theradiation sensing substrate will be described in detail below.

FIGS. 1A to 1E are cross-sectional views at various stages of forming adeep trench isolation in a radiation sensing substrate in accordancewith some embodiments of the present disclosure.

In some embodiments, as shown in FIG. 1A, a radiation sensing substrate110 is received or provided. In some embodiments, the radiation sensingsubstrate 110 includes an elementary semiconductor including silicon orgermanium in crystal, polycrystalline, and/or an amorphous structure; acompound semiconductor including silicon carbide, gallium arsenic,gallium phosphide, indium phosphide, indium arsenide, and/or indiumantimonide; an alloy semiconductor including SiGe, GaAsP, AlInAs,AlGaAs, GaInAs, GaInP, and/or GaInAsP; any other suitable material;and/or a combination thereof. In some embodiments, the radiation sensingsubstrate 110 includes a semiconductor substrate. In some embodiments,the radiation sensing substrate 110 includes a semiconductor substratedoped with p-type dopants, such as boron. In some embodiments, theradiation sensing substrate 110 includes a semiconductor substrate dopedwith n-type dopants, such as phosphorous or arsenic. In someembodiments, the radiation sensing substrate 110 includes an epitaxial(epi) layer, strained for performance enhancement. In some embodiments,the radiation sensing substrate 110 includes a silicon-on-insulator(SOI) structure. In some embodiments, the radiation sensing substrate110 is a device substrate. In some embodiments, the radiation sensingsubstrate 110 is fabricated using front-end processes.

In some embodiments, the radiation sensing substrate 110 includes afront surface 112 (also referred to as a frontside) and a back surface114 (also referred to as a backside) opposite to each other. In someembodiments, incident radiation enters the radiation sensing substrate110 through the back surface 114. In some embodiments, the radiationsensing substrate 110 includes a pixel region, a periphery region, abonding pad region and a scribe line region. For the sake of simplicity,only a portion of the pixel region in shown in FIGS. 1A to 1E. Althoughonly the portion of the pixel region is shown in FIGS. 1A to 1E, thepixel region may further include pinned layer photodiodes, photodiodegates, reset transistors, source follower transistors and transfertransistors. For the sake of simplicity, detailed structures of theabove features are not shown in FIGS. 1A to 1E.

In some embodiments, the radiation sensing substrate 110 includes aradiation sensing region (not shown). In some embodiments, the radiationsensing region is doped with dopants different from (or opposite to)dopants of the semiconductor substrate of the radiation sensingsubstrate 110. In some embodiments, the radiation sensing region isformed using one or more implantation processes or diffusion processes.In some embodiments, the radiation sensing region is formed adjacent tothe front surface 112. In some embodiments, the radiation sensingregions are operable to sense incident radiation that enters the pixelregion from the back surface 114. In some embodiments, the incidentradiation is visual light. Alternatively, the incident radiation may beinfrared (IR), ultraviolet (UV), X-ray, microwave, other suitable typesof radiation or a combination thereof.

In some embodiments, the radiation sensing substrate 110 furtherincludes an isolation region (not shown) laterally adjacent to theradiation sensing region. In some embodiments, the isolation region isdoped with dopants the same as dopants of the semiconductor substrate ofthe radiation sensing substrate 110. In some embodiments, the isolationregion is formed using one or more implantation processes or diffusionprocesses. In some embodiments, the isolation region is formed adjacentto the front surface 112.

In some embodiments, the radiation sensing substrate 110 furtherincludes an isolation feature (not shown) in the isolation region. Insome embodiments, the isolation feature is adjacent to the front surface112 of the radiation sensing substrate 110. In some embodiments, theisolation feature includes shallow trench isolation (STI) structureand/or local oxidation of silicon (LOCOS) structure. In someembodiments, some active or passive features, such as MOSFET or junctioncapacitor, are formed in the isolation region according to design needs.In some embodiments, the active or passive features in the isolationregion are protected by the isolation feature.

In some embodiments, an interconnection structure 120 is formed over thefront surface 112 of the radiation sensing substrate 110. In someembodiments, the interconnection structure 120 includes an inter layerdielectric (ILD) and multilayer interconnection (MLI) structure. In someembodiments, the interconnection structure 120 includes conductive lines122 and vias/contacts 124. Actual position and configuration of theconductive lines 122 and the vias/contacts 124 may vary depending ondesign needs and manufacturing concerns.

In some embodiments, another substrate 130 is bonded to theinterconnection structure 120. In some embodiments, the substrate 130 isa carrier substrate. In some embodiments, the substrate 130 includesapplication specific integrated circuits (ASIC). In some embodiments,the substrate 130 is bonded to the interconnection structure 120 bydirect bonding, optical fusion bonding, metal diffusion bonding, anodicbonding or other suitable bonding techniques. In some embodiments, thesubstrate 130 is configured to provide protection for the radiationsensing substrate 110 and the interconnection structure 120. In someembodiments, the substrate 130 is configured to provide support whenfollowing processes are performed on the back surface 114 of theradiation sensing substrate 110.

As shown in FIGS. 1A to 1B, a trench 110 a is formed in the radiationsensing substrate 110. In some embodiments, the trench 110 a is formedusing a material removal process, such as an etching process. In someembodiments, the etching process includes a dry etching process, a wetetching process or a combination thereof. In some embodiments, thetrench 110 a has a rectangular shape, a trapezoidal shape or othersuitable shape in cross-sectional view. In some embodiments, the trench110 a extends over half of the thickness of the radiation sensingsubstrate 110. The trench 110 a is used for forming the deep trenchisolation, which will be described below in detail.

As shown in FIGS. 1B to 1C, a corrosion resistive layer 220 is formed inthe trench 110 a. In some embodiments, the corrosion resistive layer 220is also formed over the back surface 114 of the radiation sensingsubstrate 110. In some embodiments, the corrosion resistive layer 220 isformed in a conformal manner covering an interior surface of the trench110 a and the back surface 114. In some embodiments, the corrosionresistive layer 220 includes titanium carbon nitride having a chemicalformula of TiC_(x)N_((2-x)). In some embodiments, x is in a range of 0.1to 0.9. In some embodiments, x is in a range of 0.2 to 0.8. In someembodiments, the corrosion resistive layer 220 includes 15 to 40 at % ofcarbon. In some embodiments, the corrosion resistive layer 220 includes15 to 40 at % of nitrogen. In some embodiments, the corrosion resistivelayer 220 includes 20 to 40 at % of titanium.

In some embodiments, forming the corrosion resistive layer 220 in thetrench 110 a includes: forming a titanium carbon nitride-containinglayer (not shown) in the trench 110 a; and performing a plasma treatmentwith hydrogen on the titanium carbon nitride-containing layer to convertthe titanium carbon nitride-containing layer to the corrosion resistivelayer 220.

In some embodiments, the titanium carbon nitride-containing layer isformed using physical vapor deposition (PVD), chemical vapor deposition(CVD), atomic layer deposition (ALD), other suitable depositiontechnique or a combination thereof. The CVD process includes plasmaenhanced chemical vapor deposition (PECVD) or low-pressure chemicalvapor deposition (LPCVD). In some embodiments, the titanium carbonnitride-containing layer is formed using CVD with titanium carbonnitride precursor and ammonia. In some embodiments, the titanium carbonnitride precursor includes tetrakis(dimethylamino)titanium (TDMAT),tetrakis(diethylamino)titanium (TDEAT), other suitable titanium carbonnitride precursor or a combination thereof.

In some embodiments, the plasma treatment with hydrogen has a plasmapower. In some embodiments, the plasma power of the plasma treatment isRF power. In some embodiments, the plasma power of the plasma treatmentis lower than 1,550 W. In some embodiments, the plasma power of theplasma treatment is lower than or equal to 1,450 W. In some embodiments,the plasma power of the plasma treatment is greater than 1,000 W. Insome embodiments, the plasma treatment is further with nitrogen. In someembodiments, the plasma treatment with hydrogen is used to performreduction of carbon. In some embodiments, the plasma treatment withhydrogen is used to adjust an amount of carbon of titanium carbonnitride of the corrosion resistive layer 220. In some embodiments, theplasma treatment with hydrogen is used to decrease an amount of carbonof titanium carbon nitride of the corrosion resistive layer 220.

In some embodiments, before the corrosion resistive layer 220 is formedin the trench 110 a, a dielectric material 210 is formed in the trench110 a. In some embodiments, the dielectric material 210 includes siliconoxide, silicon nitride, silicon oxynitride, spin on glass (SOG), low kdielectric, other suitable dielectric material or a combination thereof.In some embodiments, the dielectric material 210 includes silicon oxide.In some embodiments, the dielectric material 210 is formed using a CVDprocess or a PVD process. In some embodiments, the dielectric material210 has a thickness in a range of 200 angstroms to 1,000 angstroms. Insome embodiments, the dielectric material 210 and the corrosionresistive layer 220 in the trench 110 a are collectively referred to asthe deep trench isolation.

In some embodiments, before the dielectric material 210 is formed in thetrench 110 a, a high k metal oxide layer (not shown) is formed in thetrench 110 a. In some embodiments, the high-k metal oxide includeshafnium oxide, aluminum oxide, zirconium oxide, magnesium oxide, calciumoxide, yttrium oxide, tantalum oxide, strontium oxide, titanium oxide,lanthanum oxide, barium oxide, other suitable metal oxide or acombination thereof. In some embodiments, the high k metal oxide layeris formed using a CVD process or a PVD process. In some embodiments, thehigh k metal oxide layer, the dielectric material 210 and the corrosionresistive layer 220 in the trench 110 a are collectively referred to asthe deep trench isolation.

In some embodiments, as shown in FIG. 1C, after the corrosion resistivelayer 220 is formed in the trench 110 a, a reflective material 230 isformed in the trench 110 a and over the corrosion resistive layer 220.In some embodiments, the reflective material 230 fills the trench 110 a.In some embodiments, the reflective material 230 filled in the trench110 a is configured to extend reflected area. In some embodiments, thereflective material 230 includes tungsten, aluminum, copper, tantalum,titanium, other suitable metal or a combination thereof. In someembodiments, the reflective material 230 is formed using sputtering,electroplating, CVD, PVD or other suitable deposition technique. In someembodiments, the dielectric material 210, the corrosion resistive layer220 and the reflective material 230 in the trench 110 a are collectivelyreferred to as the deep trench isolation.

It is noteworthy that because of the corrosion resistive layer 220, theradiation sensing substrate 110 is not damaged when the reflectivematerial 230 is formed, and thus to prevent occurrence of white pixeldefects. In some embodiments, the corrosion resistive layer 220 canblock reaction gas, such as WF₆ for forming tungsten, and thus theradiation sensing substrate 110 will not be damaged.

In some embodiments, as shown in FIGS. 1C to 1D, a planarization processis performed on the reflective material 230 and the corrosive resistivelayer 220. In some embodiments, the planarization process includes achemical mechanical polish (CMP) process, a grinding process, an etchingprocess, any other suitable material removal process or a combinationthereof. In some embodiments, after the planarization process isperformed, an upper surface of the dielectric material 210 is exposed.

In some embodiments, as shown in FIGS. 1D to 1E, another dielectricmaterial 240 is formed over the dielectric material 210, the corrosionresistive layer 220 and the reflective material 230. In someembodiments, the dielectric material 240 includes silicon oxide, siliconnitride, silicon oxynitride, spin on glass (SOG), low k dielectric,other suitable dielectric material or a combination thereof. In someembodiments, the dielectric material 240 includes silicon oxide. In someembodiments, the dielectric material 240 is formed using a CVD processor a PVD process.

In some embodiments, as shown in FIG. 1E, a reflective grid 250 isformed over the dielectric material 240. In some embodiments, thereflective grid 250 is substantially or entirely aligned with the trench110 a. In some embodiments, the reflective grid 250 includes tungsten,aluminum, copper, tantalum, titanium, titanium nitride, other suitablematerial or a combination thereof. In some embodiments, the reflectivegrid 250 is formed using a deposition process, such as sputtering,electroplating, CVD, PVD, plasma or other suitable deposition technique,and a patterning process, such as photolithographic and etchingprocesses.

In some embodiments, after the reflective grid 250 is formed, aprotective layer 260 is formed over the reflective grid 250. In someembodiments, the protective layer 260 includes silicon oxide, siliconnitride, silicon oxynitride, spin on glass (SOG), low k dielectric,other suitable dielectric material or a combination thereof. In someembodiments, the protective layer 260 is formed using a CVD process or aPVD process. In some embodiments, the protective layer 260 is a lowdeposition rate resistor protection oxide (LRPO). In some embodiments,the protective layer 260 has a thickness greater than or equal to 1,000angstroms.

In some embodiments, after the protective layer 260 is performed, acolor filter layer (not shown) and a micro lens layer (not shown) aresequentially formed over the protective layer 260. The color filterlayer is configured to allow radiation with predetermined wavelengths toreach the radiation sensing substrate 110. The micro lens layer isconfigured to direct incident radiation toward the radiation sensingsubstrate 110. Alternatively, the position of the color filter layer andthat of the micro lens layer may be reversed, and thus the micro lenslayer is between the color filter layer and the protective layer 260.

Embodiments of an image sensor device will be described in detail below.In some embodiments, an image sensor device is a backside-illuminated(BSI) image-sensor device. In some embodiments, the BSI image sensordevice includes a charge-coupled device (CCD), a complementary metaloxide semiconductor (CMOS) image sensor (CIS), an active-pixel sensor(APS) or a passive-pixel sensor. In some embodiments, the image sensordevice includes additional circuitry and input/outputs that are providedadjacent to grid of pixels for providing an operation environment of thepixels and for supporting external communication with the pixels.

As shown in FIG. 1E, the image sensor device includes a radiationsensing substrate 110 and a deep trench isolation DTI. In someembodiments, the radiation sensing substrate 110 includes asemiconductor substrate. In some embodiments, the radiation sensingsubstrate 110 is a device substrate. In some embodiments, the radiationsensing substrate 110 includes a pixel region, a periphery region, abonding pad region and a scribe line region. For the sake of simplicity,only a portion of the pixel region in shown in FIG. 1E.

The radiation sensing substrate 110 includes a front surface 112 and aback surface 114 opposite to each other. In some embodiments, incidentradiation enters the radiation sensing substrate 110 through the backsurface 114. In some embodiments, the radiation sensing substrate 110includes a radiation sensing region (not shown).

The deep trench isolation DTI includes a trench 110 a and a titaniumcarbon nitride layer 220 in the trench 110 a. The trench 110 a extendsfrom the back surface 114 into the radiation sensing substrate 110. Insome embodiments, the titanium carbon nitride layer 220 in the trench110 a is in a conformal manner. In some embodiments, the titanium carbonnitride of the titanium carbon nitride layer 220 has a chemical formulaof TiC_(x)N_((2-x)), and x is in a range of 0.1 to 0.9. In someembodiments, x is in a range of 0.2 to 0.8. In some embodiments, x is ina range of 0.3 to 0.7. White pixel defects may be significantly improvedby using the titanium carbon nitride of the titanium carbon nitridelayer 220 with a chemical formula of TiC_(x)N_((2-x)), in which x is ina range of 0.1 to 0.9.

In some embodiments, the titanium carbon nitride layer 220 includes 15to 40 at % of carbon. In some embodiments, the titanium carbon nitridelayer 220 includes 20 to 40 at % of carbon. In some embodiments, thetitanium carbon nitride layer 220 includes 15 to 40 at % of nitrogen. Insome embodiments, the titanium carbon nitride layer 220 includes 20 to40 at % of nitrogen. In some embodiments, the titanium carbon nitridelayer 220 includes 20 to 40 at % of titanium. In some embodiments, thetitanium carbon nitride layer 220 includes 30 to 40 at % of titanium. Insome embodiments, in the titanium carbon nitride layer 220, a differencebetween an amount of carbon and an amount of nitrogen is lower than orequal to 10 at %. In some embodiments, in the titanium carbon nitridelayer 220, an amount of titanium is greater than an amount of carbon. Insome embodiments, in the titanium carbon nitride layer 220, an amount oftitanium is greater than an amount of nitrogen. In some embodiments, inthe titanium carbon nitride layer 220, an amount of nitrogen is greaterthan an amount of carbon.

In some embodiments, the deep trench isolation DTI further includes adielectric material 210 between the titanium carbon nitride layer 220and an interior surface of the trench 110 a. In some embodiments, thedielectric material 210 in the trench 110 a is in a conformal manner. Insome embodiments, the dielectric material 210 includes silicon oxide,silicon nitride, silicon oxynitride, spin on glass (SOG), low kdielectric, other suitable dielectric material or a combination thereof.

In some embodiments, the deep trench isolation DTI further includes ahigh k metal oxide layer (not shown) between the dielectric material 210and the interior surface of the trench 110 a. In some embodiments, thehigh k metal oxide layer in the trench 110 a is in a conformal manner.In some embodiments, the high-k metal oxide includes hafnium oxide,aluminum oxide, zirconium oxide, magnesium oxide, calcium oxide, yttriumoxide, tantalum oxide, strontium oxide, titanium oxide, lanthanum oxide,barium oxide, other suitable metal oxide or a combination thereof.

In some embodiments, the deep trench isolation DTI further includes areflective material 230 in the trench 110 a and over the titanium carbonnitride layer 220. In some embodiments, the reflective material 230fills the trench 110 a. In some embodiments, the reflective material 230includes tungsten, aluminum, copper, tantalum, titanium, other suitablemetal or a combination thereof. In some embodiments, the reflectivematerial 230 is in contact with the titanium carbon nitride layer 220.

In some embodiments, the image sensor device further includes anotherdielectric material 240 over the dielectric material 210. In someembodiments, the dielectric material 240 includes silicon oxide, siliconnitride, silicon oxynitride, spin on glass (SOG), low k dielectric,other suitable dielectric material or a combination thereof.

In some embodiments, the image sensor device further includes areflective grid 250 over the dielectric material 240. In someembodiments, the reflective grid 250 is substantially or entirelyaligned with the trench 110 a. In some embodiments, the reflective grid250 includes tungsten, aluminum, copper, tantalum, titanium, othersuitable metal or a combination thereof.

In some embodiments, the image sensor device further includes aprotective layer 260 over the reflective grid 250. In some embodiments,the protective layer 260 includes silicon oxide, silicon nitride,silicon oxynitride, spin on glass (SOG), low k dielectric, othersuitable dielectric material or a combination thereof.

In some embodiments, the image sensor device further includes a colorfilter layer (not shown) and a micro lens layer (not shown) over theprotective layer 260. The color filter layer is configured to allowradiation with predetermined wavelengths to reach the radiation sensingsubstrate 110. The micro lens layer is configured to direct incidentradiation toward the radiation sensing substrate 110.

In some embodiments, the image sensor device further includes aninterconnection structure 120 over the front surface 112 of theradiation sensing substrate 110. In some embodiments, theinterconnection structure 120 includes an inter layer dielectric (ILD)and multilayer interconnection (MLI) structure. In some embodiments, theinterconnection structure 120 includes conductive lines 122 andvias/contacts 124, which may be coupled to various doped features,circuitry and input/output of the image sensor device.

In some embodiments, the image sensor device further includes anothersubstrate 130 over the interconnection structure 120. In someembodiments, the substrate 130 is a carrier substrate. In someembodiments, the substrate 130 is an application specific integratedcircuits (ASIC) substrate.

According to some embodiments, a method of forming a deep trenchisolation in a radiation sensing substrate includes: forming a trench inthe radiation sensing substrate; forming a corrosion resistive layer inthe trench, in which the corrosion resistive layer includes titaniumcarbon nitride having a chemical formula of TiC_(x)N_((2-x)), and x isin a range of 0.1 to 0.9; and filling a reflective material in thetrench and over the corrosion resistive layer.

According to some embodiments, a method of forming a deep trenchisolation in a radiation sensing substrate includes: forming a trench inthe radiation sensing substrate; forming a titanium carbonnitride-containing layer in the trench; and performing a plasmatreatment with hydrogen on the titanium carbon nitride-containing layerto convert the titanium carbon nitride-containing layer to a corrosionresistive layer; and filling a reflective material in the trench andover the corrosion resistive layer.

According to some embodiments, an image sensor device includes aradiation sensing substrate and a deep trench isolation. The radiationsensing substrate has a front surface and a back surface. The deeptrench isolation is in the radiation sensing substrate. The deep trenchisolation includes a trench extending from the back surface into theradiation sensing substrate and a titanium carbon nitride layer in thetrench.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method of forming deep trench isolation in aradiation sensing substrate, comprising: forming a trench in theradiation sensing substrate, the trench extending from a back surface ofthe radiation sensing substrate into the radiation sensing substrate;and forming a corrosion resistive layer in the trench, wherein thecorrosion resistive layer comprises titanium carbon nitride.
 2. Themethod of claim 1, wherein the titanium carbon nitride has a chemicalformula of TiCxN(2−x).
 3. The method of claim 2, wherein x is in a rangeof 0.1 to 0.9.
 4. The method of claim 3, comprising: filling areflective material over the corrosion resistive layer.
 5. The method ofclaim 1, comprising: filling a reflective material over the corrosionresistive layer.
 6. The method of claim 1, comprising: forming adielectric material in the trench before forming the corrosion resistivelayer in the trench.
 7. The method of claim 1, wherein forming thecorrosion resistive layer in the trench comprises: forming a titaniumcarbon nitride-containing layer in the trench; and performing a plasmatreatment with hydrogen on the titanium carbon nitride-containing layerto convert the titanium carbon nitride-containing layer to the corrosionresistive layer.
 8. The method of claim 1, comprising: forming aninterconnection structure comprising a conductive line over a frontsurface of the radiation sensing substrate before forming the trench inthe radiation sensing substrate.
 9. The method of claim 8, comprising:attaching a second substrate to the interconnection structure beforeforming the trench in the radiation sensing substrate, wherein theinterconnection structure is disposed between the radiation sensingsubstrate and the second substrate.
 10. The method of claim 9, whereinthe second substrate comprises an application specific integratedcircuit (ASIC).
 11. The method of claim 1, wherein the corrosionresistive layer comprises: 15 to 40 at % carbon, 15 to 40 at % nitrogen,and 20 to 40 at % titanium.
 12. The method of claim 1, wherein formingthe corrosion resistive layer in the trench comprises: forming thecorrosion resistive layer using a titanium carbon nitride precursor andammonia, wherein the titanium carbon nitride precursor comprises atleast one of tetrakis(dimethylamino)titanium (TDMAT) ortetrakis(diethylamino)titanium (TDEAT).
 13. The method of claim 1,comprising: forming a dielectric material in the trench before formingthe corrosion resistive layer in the trench, wherein forming thecorrosion resistive layer in the trench comprises forming the corrosionresistive layer over the dielectric material to conceal the dielectricmaterial; and exposing a portion of the dielectric material afterforming the corrosion resistive layer in the trench.
 14. The method ofclaim 1, comprising: forming a dielectric layer over the corrosionresistive layer; forming a reflective grid over the dielectric layer,wherein the reflective grid comprises a reflective structure overlyingthe trench; and forming a protective layer over the reflectivestructure.
 15. A method of forming deep trench isolation in a radiationsensing substrate, comprising: forming a trench in the radiation sensingsubstrate; forming a titanium carbon nitride-containing layer in thetrench; and performing a plasma treatment with hydrogen on the titaniumcarbon nitride-containing layer to convert the titanium carbonnitride-containing layer to a corrosion resistive layer.
 16. The methodof claim 15, comprising: forming a reflective grid over the corrosionresistive layer, wherein the reflective grid comprises a reflectivestructure overlying the trench; and forming a protective layer over thereflective structure.
 17. The method of claim 15, comprising: filling areflective material over the corrosion resistive layer.
 18. The methodof claim 15, comprising: forming a conductive line over a front surfaceof the radiation sensing substrate before forming the trench in theradiation sensing substrate.
 19. A method of forming deep trenchisolation in a radiation sensing substrate, comprising: forming a trenchin the radiation sensing substrate; forming a dielectric layer over theradiation sensing substrate and in the trench; and forming a corrosionresistive layer in the trench over the dielectric layer to sandwich thedielectric layer between the radiation sensing substrate and thecorrosion resistive layer.
 20. The method of claim 19, comprising:forming a second dielectric layer over the corrosion resistive layer,wherein the second dielectric layer contacts the dielectric layer.